Chimeric antigen receptor macrophages (CAR-M) sensitize HER2+ solid tumors to PD1 blockade in pre-clinical models

We previously developed human CAR macrophages (CAR-M) and demonstrated redirection of macrophage anti-tumor function leading to tumor control in immunodeficient xenograft models. Here, we develop clinically relevant fully immunocompetent syngeneic models to evaluate the potential for CAR-M to remodel the tumor microenvironment (TME), induce T cell anti-tumor immunity, and sensitize solid tumors to PD1/PDL1 checkpoint inhibition. In vivo, anti-HER2 CAR-M significantly reduce tumor burden, prolong survival, remodel the TME, increase intratumoral T cell and natural killer (NK) cell infiltration, and induce antigen spreading. CAR-M therapy protects against antigen-negative relapses in a T cell dependent fashion, confirming long-term anti-tumor immunity. In HER2+ solid tumors with limited sensitivity to anti-PD1 (aPD1) monotherapy, the combination of CAR-M and aPD1 significantly improves tumor growth control, survival, and remodeling of the TME in pre-clinical models. These results demonstrate synergy between CAR-M and T cell checkpoint blockade and provide a strategy to potentially enhance response to aPD1 therapy for patients with non-responsive tumors. Anti-PD1 monotherapy shows limited efficacy against HER2+ tumors. Here, the authors show that murine CAR macrophages (CAR-M) induce tumor microenvironment remodeling, T-cell mediated immunity and synergy with PD1 blockade, improving survival in immunocompetent female-mouse models of HER2+ solid tumors.

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